Lucerne - a serious option

Published 22 May 15

Lucerne is enjoying a renaissance due to its high yield and crude protein content (17-22%). It is also rich in minerals and vitamins, and complements maize and grass silage, as its structural fibre aids ruminant digestion, reducing the risk of acidosis.

Interest in this leafy, tall legume has waxed and waned over the past 50 years in line with the weather. In droughty seasons and areas where low summer rainfall is the norm, lucerne comes into its own as its long tap root allows it to find water and maintain growth even in the driest times.

This main root stores nutrients, which helps the plant regrow after defoliation, allowing multiple cuts or grazings. Nodules on the roots contain bacteria that can fix up to 250kg nitrogen (N) /ha/year, so the crop needs no additional N fertiliser.

Fresh weight production, after the first year, can be up to 40t/ha/year (16t/acre). Target annual dry matter (DM) yield (at 30% DM for silage) should be around 12t DM/ha (4.8t DM/acre).

Lucerne likes to be grown on free-draining soils and is usually used as a five-year crop, but it will not thrive in wet or waterlogged ground. It is also sensitive to weed competition in its first year.

Which varieties?

The most important characteristic to consider is dormancy – which is a measure of winter hardiness on a scale of 1 (very dormant) to 12 (no dormancy).

For UK conditions and to achieve three to four cuts a year, a dormancy rating of 4-5 is about right. The Lucerne Descriptive List is now available in the RGCL for 2015-2016, and the DairyCo publication Growing and Feeding Lucerne provides best practice advice on the growing and feeding of Lucerne for dairy cattle.

Grazing and conserving

Lucerne can be grazed but great care is needed not to damage the crown where the growing points sit. Rotational grazing is much kinder than set stocking as it allows a recovery time. Never let sward height fall below 6-7cm.

Lucerne silage can be clamped or baled, but its low sugar content can make it difficult to ensile. Wilting is advisable to a minimum DM of at least 30%, as is the use of an additive.

Up to 70% of the protein and 90% of the vitamins and minerals are in the leaf, so it is important to minimise leaf loss. The crop must not be over wilted or roughly handled at harvest and pick-up.